An optical fiber ribbon is a collection of several small optical fibers arranged side-by-side, all lying in a plane, encapsulated within a matrix made of a synthetic resin. This flat, side-by-side arrangement allows packing many optical fibers in a small cross-sectional area.
Sometimes one of the optical fibers in a ribbon needs to be repaired while the other fibers in the ribbon remain available to carry light signals. To repair a damaged optical fiber without disturbing any live fibers, the matrix must be removed from the optical fibers allowing access to the one or more fibers that must be repaired. Another, more frequent reason for accessing individual fibers in a ribbon is to splice one fiber to connect it to a piece of terminal equipment, leaving the other fibers intact until the ribbon is laid to another piece of terminal equipment. There is therefore a need to be able to remove the matrix from an optical fiber ribbon along a length of the ribbon not necessarily starting at an end of the ribbon.
Several methods have been developed of removing the matrix of an optical fiber ribbon for some interior span to access the individual fibers encapsulated by the ribbon matrix. These methods include cutting or scraping off the matrix, or partially cutting (scoring) the matrix, and then mechanically removing it from the fibers. All of these methods, it is found, are likely to cause damage to the optical fibers, and so are undesirable.
Another method involves shearing the matrix in some fashion, such as bending, tearing, pinching, or fatiguing it, to peel it away from the optical fibers. These methods mechanically disturb the fibers of the ribbon well beyond the region where access is required; this rearranging the fibers decreases the packing density, compared to what is possible with the fibers arranged in the ribbon as originally manufactured.
Another method uses adhesive tape and, optionally, a strong liquid adhesive. Here the section of the optical fiber ribbon bearing the optical fibers to be accessed is pressed onto an adhesive tape and then pulled off the tape, leaving behind at least some of the matrix from the span of ribbon to be stripped. Sometimes a strong liquid adhesive, such as a cyanoacrylate, is used with the tape. The strong liquid adhesive is applied at the point on the ribbon where entry is desired. That point on the ribbon is then pressed onto a surface adjacent the adhesive tape. Finally, the optical fiber ribbon is pulled up and away, the strong liquid adhesive ensuring that the matrix will tear and at least some will remain behind, adhered to the tape.
In this method, the prior art teaches using double-sided tape and a separate thin panel on which the strong liquid adhesive is deposited and to which the ribbon at the desired point of entry is glued. This method suffers from at least two drawbacks. First, there must be in the immediate vicinity a substantially flat and clean surface onto which the double-sided adhesive tape can be adhered. Second, since the panel on which the strong liquid adhesive is deposited will have some thickness, there will be a length of ribbon not adhered to the double-sided tape between where the ribbon is glued and where it first adheres to the tape. So when the ribbon is pulled away from where it is glued there will be a slight jerk, tending to remove the ribbon from the tape without further removing the matrix from the fibers. In addition, after removing the ribbon matrix from the fibers, the double-sided tape must be removed from the surface it was pressed onto. This residue of tape and matrix can be difficult to remove from the surface bearing the tape, making cleanup challenging.
Another method uses a solvent to soften or weaken the matrix material so that it falls away or is easily peeled away from the optical fibers. This method, however, tends to remove the coating of the optical fibers which is often color coded, and, in addition, often requires great patience. However, a method based on this approach could avoid mechanically stressing the optical fibers to be accessed. Yet the prior art based on this approach uses an abrasive scrub-pad to remove the matrix. Using a scrub-pad places stress on the optical fibers within the optical fiber ribbon, increasing the chance that a fiber will break as it ages or otherwise unacceptably degrade.
Solvent-based methods are discussed in U.S. Pat. No. 4,147,407 to Eichenbaum, which notes that the prior art teaches solvent stripping of the coating of a coated fiber or ribbon. Solvent-based methods are also discussed in U.S. Pat. No. 5,604,834 to Beasley, which teaches that efforts have been made to gain midspan entry by soaking optical ribbon fiber in a solvent gel and then wiping off the solvent matrix material with a rough pad or the like, but the shortcomings of this method make it commercially unacceptable; using a solvent is said to be messy, time-consuming, unreliable, limited to a relatively short region of midspan entry, and to discolor optical fibers.
For a solvent-based approach that would make possible access with less stress to the optical fibers, what is needed is a way to eliminate any abrasive scrubbing of the optical fiber and so reduce the chance that an optical fiber within the ribbon will be damaged. In addition, a method or kit based on using a solvent should allow a technician to observe the progress of the solvent in softening the matrix of the optical fiber ribbon, instead of working in the blind. This would allow the technician to remove the solvent from the optical fiber ribbon as soon as the solvent has softened the matrix enough for it to be removed, instead of possibly waiting so long that the solvent damages the encapsulated optical fibers. Finally, what is needed is a less messy way of using a solvent, so that when the solvent is applied to an optical fiber ribbon, the solvent will not likely drip off the optical fiber ribbon onto nearby optical fiber ribbons and soften the matrix of those ribbons.